The construction of insulated, electrical conductors, i.e. wires and cables, designed for medium to high voltage applications is well known in the art and commonly comprises a core conductor of one or more strands of a conducting metal or alloy such as copper, a layer of semi-conductive shielding, a layer of insulation, such as crosslinked polyethylene, and a layer of semi-conductive insulation shielding, overlying the insulation. A plurality of neutral wires which are usually made of copper may be embedded in or wrapped around the layer of semi-conductive insulation shielding, if desired, in the form of a concentric ring around the insulated cable.
The formation of crosslinking bonds between the insulation and shielding makes subsequent separation of the two layers (insulation and semi-conductive shielding) such as occurs in making splices or terminal connections, very difficult and time consuming. Such a strong bond also makes the semi-conductive layer prone to leave carbon residues on the insulation even when it is finally peeled off. Accordingly, a strippable semi-conductive shielding which can be easily and cleanly stripped from the insulation of an insulated conductor is therefore very desirable in this art.
Thus, it is an object of this invention to provide a vulcanizable semi-conductive insulation shielding composition which is particularly useful for providing a strippable shielding for insulated electrical conductors, e.g. wires and cables, that contain, as the primary insulation, a crosslinked polyolefin. Another object of this invention is to provide an article of manufacture comprising the crosslinked product of said vulcanizable semi-conductive insulation shielding composition bonded directly to a crosslinked polyolefin substrate. Yet another object of this invention is to provide an article of manufacture, as defined above, wherein said crosslinked polyolefin is the primary insulation of an insulated electrical conductor, thus providing insulated electrical conductors, e.g. wires and cables comprising, as the primary insulation, a crosslinked polyolefin and as the insulation shield, an easily strippable crosslinked semi-conductive composition. Other objects and advantages of this invention will become readily apparent from the following description and appended claims.